What characteristics are common in all mammals?

There is many but some main ones are that we breathe oxygen , were warm blooded, we have hair , give live birth and breastfeed

There are several characteristics that classify mammals as mammals, here are the main ones:

Breath air

Vertebral Column

Reproduce live offspring

Have hair or fur

Warm-Blooded

Produce milk

(Others):

Single boned jaw

4 chambered hearts

3 bones in middle ear

1 time tooth replacement (at least) - For example, elephants and manatees have "marching molars".

Diaphragms

primary succession occurs in essentially lifeless areas regions in which the soil is incapable of sustaining life as a result of such factors as lava flows, newly formed sand dunes, or rocks left from a retreating glacier. secondary succession occurs